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Section Date Name 10.1 Temperature, Thermal Energy, and Heat Summary Textbook pages 424-435 Before You Read We often use the terms heat and temperature interchangeably. Do you think they mean the same thing? Explain your reasoning in the lines below. How is energy associated with moving particles? The kinetic molecular theory explains that particles in matter are in constant motion. Kinetic energy is the energy of a particle or an object due to its motion. When particles collide, kinetic energy is transferred between them. The particles of a substance move at different speeds depending on the state of the substance. The particles of a gas have more kinetic energy than those of a liquid and move more quicldy. The particles of a liquid have more kinetic energy than those of a solid. Kinetic energy is not the only energy associated with moving particles. Potential energy is stored energy that has the potential to be transformed into another form of energy, such as kinetic energy. A good example is the gravitational attraction between Earth and the textbook you are holding. As you lift the textbook, its gravitational potential energy increases. The book has a greater distance to fall, so more energy will be transformed into kinetic energy if it does. On the other hand, the lower you hold the book, the less gravitational potential energy it has. At a lower height, less energy will be transformed into kinetic energy if the book falls. Similarly, there are attractive electrical forces between atoms and molecules. The pull of these attractive forces also gives particles potential energy. ® Mark the Text Check for Understanding As you read this section, be sure to reread any parts you do not understand. Highlight any sentences that help make concepts clearer for you. Reading Check What two types of energy are associated with moving particles? How is kinetic energy measured? Kinetic energy is measured in terms of temperature, thermal energy, and heat. 1. Temperature is a measure of the average kinetic energy of all the particles in a sample of matter. As the particles’ © 2008 McGraw-Hill Ryerson Limited Section 10.1 Temperature, Thermal Energy, and Heat • MHR 177 Section 10.1 Summary continued average kinetic energy increases, the temperature of the sample also increases, and vice versa. For example, particles in a glass of cold water move more slowly than, and therefore have less kinetic energy than, particles in a cup of hot water. Three different scales are used to measure temperature: Fahrenheit, Celsius, and Kelvin. water boils 212°F 100°C 373 K water freezes 32°F 0°C 273K absolute zero -. -459°F,. —273°C, ) Fahrenheit \. ) Celsius = *0K Kelvin 2. Thermal energy is the total energy of all the particles in a solid, liquid, or gas. A hot bowl of soup has more thermal energy when it is first served than after it cools. So far this is similar to temperature. However, since thermal energy includes the energy of all of the particles in a sample of matter, a large bowl of soup has more thermal energy than a small bowl of soup at the same temperature. In fact, a swimming pooi of lukewarm water has more thermal energy than a small cup of hot tea. 3. Heat is the amount of thermal energy that transfers from an area or object of higher temperature to an area or object of lower temperature. Heat can be transferred in three ways: 1. Conduction: Conduction describes heat transfer that occurs when faster moving particles collide with slower moving particles. During conduction, heat is transferred from matter with a higher temperature and greater kinetic energy to matter with a lower temperature and less kinetic energy. For example, if a metal spoon that is at room temperature is placed in a pot of boiling water, heat will be transferred to the spoon by conduction and it will become hot. Materials often conduct heat at different rates. Metals, for example, are good thermal conductors, while wood and air are not. 178 MHR • Section 10.1 Temperature, Thermal Energy, and Heat © 2008 McGrawHilI Ryerson Limited Section Name Summary continued 2. Convection: Convection is the transfer of heat within a fluid, where the fluid actually moves from one place to another. Unlike conduction, convection transfers matter as well as heat. A boiling pot of water provides a good example of how convection works. As the water at the bottom of the pot heats up, the molecules begin to move faster and their kinetic energy increases, causing them to spread apart. The water expands and becomes less dense than the surrounding water. As a result, it rises to the surface, where it cools, contracts, and sinks— only to be reheated and circulated again. This movement of a fluid due to differences in density is called a convection current. 3. Radiation: Radiation is the transfer of heat by electromagnetic waves that carry radiant energy. One type of radiation associated with heat transfer is called infrared radiation, or heat radiation. This is the heat transfer you experience when you stand close to a campfire. The campfire is emitting electromagnetic waves toward your body, causing you to feel warmth. Similarly, everything around you experiences heat transfer as a result of solar radiation from the Sun, which includes many different types of electromagnetic waves. Reading Check What is the difference between convection and radiation? What are Earth’s energy sources? Earth receives energy from three main sources: 1. Solar radiation, including visible light, infrared radiation, and other types of radiation, comes from the Sun. 2. Residual thermal energy from when Earth was formed is slowly released. 3. Decay of underground radioactive elements produces energy. © 2008 McGraw-Hill Ryerson Limited Section 10.1 k 1 0. 1 1 Date Temperature, Thermal Energy, and Heat • MHR 179 Name Section Date 12.1 Evidence for Continental Drift Summary Textbook pages 506-517 Before You Read Scientists did not accept the continental drift theory for a long time. Why do you think this was the case? Write your ideas in the lines below. Mark the Text In Your Own Words After you read this section, explain the evidence for the continental drift theory in your own words. Reading Check Millions of years ago, all the continents were joined as a “supercontinent.” What was it called? What is continental drift? In the early 20th century, German scientist Alfred Wegener proposed the continental drift theory, which argues that the continents “drifted” to their present locations over millions of years. On a world map, the curves of South America’s eastern coastline and Africa’s western coastline seemed to match, giving Wegener his first piece of evidence for continental drift. The fit suggested that, millions of years ago, all the continents were joined as a “supercontinent” named Pangaea (from the Greek words pan, meaning all, and gaea, meaning Earth). Wegener also noted that regions of some continents that are far apart have similar rocks, mountain ranges, fossils, and patterns of paleoglaciation (evidence of ancient glaciers and the rock markings they left behind). How do continents move? After Wegener’ s death, scientists discovered that the surface of Earth is broken into tectonic plates, large, movable slabs of rock that slide over a layer of partly molten rock. According to plate tectonic theory, when tectonic plates move across Earth’ s surface, they carry the continents with them. Many volcanoes and earthquake zones on a map reveal the boundaries between the plates. Chains of volcanic islands, such as the Hawaiian Islands, reveal where tectonic plates have passed over geological hot spots—areas where molten rock has risen to Earth’s surface. This idea was first suggested by Canadian scientist I. Tuzo Wilson. © 2008 McGraw-Hill Ryerson Limited Section 12.1 Evidence for Continental Drift • MHR 207 continued The process of sea floor spreading, first proposed by Harry Hess, provides a mechanism for continental drift. This process involves magma, molten rock from beneath Earth’s surface. Because it is molten, magma is less dense than the surrounding rock. Thus, magma rises and breaks through Earth’s crust in certain weak areas. One such place is a spreading ridge, a gap in the sea floor that is gradually widening as tectonic plates move apart. Magma cools and hardens as it intrudes into this gap, pushing older rock aside as it creates new sea floor. The largest of all spreading ridges, and the first one discovered, is the Mid-Atlantic Ridge, a mountain range running north to south down the length of the Atlantic Ocean. The evidence for sea floor spreading includes the following: 1. Age of ocean rocks: The youngest rocks are found closest to the ridge, indicating that new rock is being formed. Reading Check List one observation that provides evidence for sea floor spreading. 2. Sediment thickness: The layer of ocean sediment—the small particles of silt and organic debris deposited on the ocean floor—becomes thicker the farther it is from the ridge. This indicates that the sea floor is older and farther away from the ridge. 208 MHR • Section 12.1 Evidence for Confinental Drift © 2008 McGraw-Hill Ryerson Limited continued 3. Magnetic striping: At a spreading ridge, iron containing minerals in the magma align themselves with Earth’s magnetic field as the magma cools. Because the orientation of Earth’s magnetic field has switched many times over history, rocks on the sea floor exhibit both normal polarity and reverse polarity, depending on when they cooled. When scientists used a magnetometer, a device that detects variations in magnetic fields, they found a pattern of alternating polarity repeated on both sides of the Mid-Atlantic Ridge, as shown below. This phenomenon, known as magnetic striping, indicates that new rock is being laid down on the sea floor. S © 2008 McGraw-Hill Ryerson Limited Normal magnetic polarity Reverse magnetic polarity Section 12.1 Evidence for Continental Drift • MHR 209 Name Section Date 12.2 Features of Plate Tectonics Summary Textbook pages 518-53 7 Before You Read Earthquakes frequently occur in British Columbia. State what you already know about earthquakes in the lines below. What lies below Earth’s surface? Mark the Text Earth is made of four layers with distinct characteristics. The crust is Earth’s outermost layer. It is made from solid, brittle rock and is 5—70 km thick. The mantle is Earth’s thickest layer. The upper mantle (660 km thick) is composed of partly molten rock that flows like thick toothpaste. A transition zone separates it from the lower mantle (about 2300 km thick), which is made of solid, dense material including magnesium and iron. Below the mantle lies the liquid outer core (about 2300 km thick and mostly nickel and iron). The inner core with a radius of 1200 km lies at Earth’s centre. The incredible pressure at Earth’s centre keeps the iron and nickel in the inner core solid. Scientists believe that the inner and outer cores rotate at different speeds, producing Earth’s magnetic field. Identify Definitions As you read this section, highlight the definitions of the words that appear in bold print. 0 Reading Check List the four layers that make up Earth. What are tectonic plates? Tectonic plates are large, rigid, but mobile plates of rock. There are about 12 major tectonic plates and many smaller ones. Made up of the crust and the uppermost mantle, they form the lithosphere. Oceanic plates contain dense basalt rock. Continental plates contain large amounts of granite. Below the lithosphere lies the asthenosphere, a partly molten layer in the upper mantle. Radioactive decay in some parts of the asthenosphere heats the mantle in these regions. Convection currents result as these hotter, and therefore less dense, regions of the mantle rise, cool, and sink again, only to be reheated. This mantle convection is one of the driving forces behind plate movement. 214 MHR • Section 12.2 Features of plate tectonics 0 Reading Check Name the process in the asthenosphere that pushes magma to Earth’s surface, causing tectonic plates to move. © 2008 McGraw-Hill Ryerson Limited Section Name 1 2.2 h— Date continued How do tectonic plates interact? A region where two tectonic plates are in contact is known as a plate boundary. The way in which tectonic plates interact depends on the type of plates and the direction the plates are moving relative to one another. There are three main types of plate interactions:. 1. Divergence : Divergent plate boundaries mark the areas where tectonic plates are spreading apart. Such plates, for example, the East African Rift, are known as diverging plates. Rising currents of magma cool as they reach the surface and become “new” rock, resulting in spreading centres. A spreading centre in the ocean is called a spreading ridge or oceanic ridge. On land, it is called a rift valley. As new material at a ridge or rift pushes older material aside, the tectonic plates move away from the ridge. This process is called ridge push. Rift eruptions may occur when magma erupts at divergent plate boundaries. The Juan de Fuca ridge is an example. 2. Convergence A convergent plate boundary occurs where tectonic plates collide. Such plates are known as converging plates. If a dense oceanic plate collides with a continental plate, the heavy oceanic plate will dive under the lighter continental plate in an event known as subduction. A deep underwater valley, called a trench, forms where the plates make contact. As the edge of a tectonic plate subducts, it pulls the rest of the plate with it. This process is called slab pull. Along with convection currents and ridge push, slab pull helps keep tectonic plates in motion. As subduction occurs, magma can break through to the surface, forming volcanoes. A long chain of volcanoes, called a volcanic belt, may form as a result. The force of the collision between oceanic and continental plates also creates mountain ranges as the continental rock crumples and bends. British Columbia’s Coast Mountains and Cascade Mountain Range were produced by such collisions. © 2008 McGraw-Hill Ryerson Limited Section 12.2 Features of plate tectonics • MHR 215 Section Name Date 1 2.2 [— continued Most volcanoes in volcanic belts are composite volcanoes, such as Mount Garibaldi, in British Columbia. Their cone shape results from repeated eruptions of ash and lava. Shield volcanoes are the world’s largest, and their shape resembles a shield. They are not formed when plates collide, but when weaker areas of the lithosphere move over a “hot spot”. The Anahim Belt is a chain of shield volcanoes in British Columbia. Rift volcanoes, like the Krafla volcano in Iceland, are formed when magma erupts through long cracks in the lithosphere. Subduction also occurs where two oceanic plates converge. Cooling causes one plate to become denser. The denser plate slides deep into the mantle. Such convergence may produce a long chain of volcanic islands known as a volcanic island arc. The Aleutian islands and the islands of Japan are examples of a volcanic island arc. Subduction does not occur when two continental plates collide since the plates have similar densities. As continental plates collide, their edges fold, forming large mountain ranges, such as the Himalayas. 3. Transform : Convection currents in the mantle often cause tectonic plates to slide past each other. Such regions are known as transform plate boundaries. Earthquakes and faults (breaks in rock layers due to movement on either side) may result. A fault that occurs at a transform plate boundary is known as a transform fault. The San Andreas Fault is an example of a transform plate boundary. How are tectonic plates linked to earthquakes? Friction between moving tectonic plates often works against convection currents, producing stress (the build-up of pressure). When the plates can no longer resist the stress, there is an earthquake—a massive release of energy that shakes the crust. The focus is the location inside Earth where an earthquake starts. The epicentre is the point on Earth’s surface directly above the focus. An earthquake with a shallow focus (0—70 1cm) typically creates more damage than one with an intermediate focus (70—300 1cm), or a deep focus (greater than 300 km), as energy release occurs closer to the surface. 216 MHR • Section 12.2 Features of plate tectonics © 2008 McGraw-Hill Ryerson Limited Section Name 1 2.2 L— Date continued Energy released by an earthquake produces vibrations known as seismic waves. Seismology is the study of earthquakes and seismic waves. There are three types of waves: primary waves (P-waves) and secondary waves (S-waves), both of which travel underground, and surface waves (L-waves), which roll along Earth’s surface. Scientists use a seismometer to measure seismic waves. With each 1-step increase on the magnitude scale, the seismic waves are 10 times larger. Earthquakes can be felt if they are over magnitude 2.0. Over magnitude 6.0, they can damage building. P-waves are the fastest and stretch in the direction of the wave, like a spring. They can travel through solids, liquids, and gases. S-waves are slower, and move perpendicularly to the direction of the wave. They travel through solids but not liquids. L-waves are the slowest and cause a rolling motion like ripples on the ground. © 2008 McGraw-Hill Ryerson Limited Section 12.2 Features of plate tectonics • MHR 217